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            let arr=[1,2,3,4,5,6,7,6,5,4,3,2,1];
            //1.数组去重
            /*
            let result=[...new Set(arr)];
            console.log(result);
            */
            //2.交集
            let arr2=[3,4,5,6,5,4,3];
            /*
            let result=[...new Set(arr)].filter(item=>{
                let s2=new Set(arr2);
                if(s2.has(item))
                {
                    return true;
                }
                else
                {
                    return false;
                }
            });
            */
            //let result=[...new Set(arr)].filter(item=>new Set(arr2).has(item));
            //console.log(result);
            //3.并集
            let union=[...new Set([...arr,...arr2])];
            console.log(union);
            //4.差集
            let diff=[...new Set(arr)].filter(item=>!(new Set(arr2).has(item)));
            console.log(diff);
        };
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